The present invention relates to a vehicle occupant protection apparatus. In particular, the present invention relates to an air bag having a vent that can be selectively opened to discharge inflation fluid.
It is known to provide an air bag with a vent. The vent opens, or is uncovered, when the air bag inflates to help protect a vehicle occupant, to discharge inflation fluid from the inflated air bag. In some air bags, the vent may be selectively opened depending on sensed factors, for example, whether the occupant""s seat belt is buckled. U.S. Pat. No. 6,290,257 shows one such air bag.
The present invention in one embodiment relates to a vehicle occupant protection apparatus comprising an inflatable vehicle occupant protection device having a deflated condition and an inflated condition. The device has a portion defining a vent opening for enabling flow of inflation fluid out of the device. The apparatus includes a patch for covering the vent opening to block flow of inflation fluid out of the device through the vent opening. The apparatus also includes an inflator for directing inflation fluid into the device to inflate the device from the deflated condition to the inflated condition. A release thread sewn between the patch and the device releasably secures the patch to the protection device to close the vent opening. Sensor means senses a condition requiring venting of inflation fluid from the device when the device inflates. A holding mechanism has a first condition in response to the sensor means sensing a condition requiring venting of inflation fluid from the device, and a second condition in response to the sensor means not sensing a condition requiring venting of inflation fluid from the device. The holding mechanism when in the first condition holds the release thread so that at least a portion of the release thread pulls away from the patch and the device, when the device inflates, thereby releasing the patch to open the vent opening. The holding mechanism when in the second condition releases the release thread for movement with the patch in a direction away from the holding mechanism, when the device inflates.
In another embodiment, the present invention relates to a release thread that closes the vent opening when the protection device is in the deflated condition. The apparatus includes a clamp having a first condition clamping the release thread and a second condition not clamping the release thread. A controller controls operation of the clamp to cause the clamp to take the first condition in response to the sensor means sensing a condition requiring venting of inflation fluid from the device when the device inflates. The clamp takes the second condition in response to the sensor means not sensing a condition requiring venting of inflation fluid from the device when the device inflates.